Commercial fishing is a worldwide enterprise that involves the capture of ocean and
freshwater fish, shellfish, and marine mammals, and their processing for
market. There are several major companies that do this. The names of some of
these companies are: Atlantic Ocean Fisheries, Pacific Ocean Fisheries, and
the Inland Fisheries. Fishing equipment ranges from small boats whose nets
are cast and hauled in by hand to factory ships equipped with the most
advanced technologies for finding, harvesting, and processing huge quantities
of fish. These large catches are made at heavy expense, not only in the cost
of the equipment and fuel, but also in the potential depletion of fishery
resources. There is on the job training required for the operation of the
machinery.
The major portion of the total fish harvest consists of relatively few ocean
species, which are divided into two groups. Pelagic species, those which
inhabit the near-surface layers of the oceans, include several species of
herring, tuna, salmon, anchovies, pilchard, sardines, menhaden, and mackerel.
Demersal species, fish that inhabit the areas near the ocean bottom include,
cod, sole, halibut, haddock, hake, and flounder. Large catches are also made
of a group of fish classed commercially as shellfish-shrimp, lobster,
scallops, oysters, clams, crabs, mussels, and squid.
Almost all large Pelagic and Demersal fish catches are made over the
continental shelf, the underwater plateau surrounding the continents and large
islands. In these waters temperatures, water depths, and the currents that
influence the quantities of available food create an environment that is
highly favorable to the existence of large schools of fish.